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DMS - Unified Modelling Language

12/10/20

UML: A specification defining a graphical language for visualising, specifying, constructing and documenting the artefacts of distributed object systems.

Latest version: 2.6

Benefits of UML

  • Enhances communication and ensures the right communication
  • Captures the logical software architecture independent of the implementation language.
  • Helps to manage the complexity
  • Enables reuse of design

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Object Orientated Analysis

Use case diagrams

  • Describe a set of actions that some system should or can perform in collaboration with one or more external users of the system.
  • No attempt to represent an order or a number of executions.

Use case diagram components

Actors - Entities that interface with the system. Can be people or other systems.

Use case - Based on user stories and represent what the actor wants your system to do for them. In the use case diagram only the use case name is represented.

Subject - Classifier representing a business, software system, physical system or device under analysis design, or consideration.

Relationships

Relationships between use case and actor

  1. Association indicates which actor indicates which use case

Relationship between two use cases

  1. Specifying common functionality and simplifying use case flows
  2. Using <> or <>

<<include>>- multiple use cases share a piece of same functionality which is placed in a separate use case.

<<extend>> - Used when activities might be performed as part of another activity but are not mandatory for a use case to run successfully.

Use case diagram of a fleet logistics management company

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Base Path - The optimistic path (best case scenario)

Alternative Path - Every other possible way the system can be used/abused. Includes perfectly normal alternate use, but also errors and failures.

Use Case: Borrow copy of book

Purpose: The book borrower (BB) borrows a book from the library using the Library Booking System (LBS)

Pre-conditions:

  1. The book must exist
  2. The book must be available

Base Path:

  1. LBS requests membership card
  2. BB provides membership card
  3. BB is logged in by LBS
  4. LBS checks permissions / debts
  5. LBS asks for presenting a book
  6. BB presents a book
  7. LBS scans RFID tag inside book
  8. LBS updates records accordingly
  9. LBS disables anti-theft device
  10. BB is logged out by LBS
  11. LBS confirms that process has been completed successfully

Alternative Path

  1. BB's card has expired: Step 3a: LBS must provide a message that card has expired; LBS must exit the use case

Post conditions for base path

Base path - BB has successfully borrowed the book & system is up to date.

Alternate Path 1 - BB was NOT able to borrow the book & system is up to date.